1. Field of the Invention
This invention relates in general to a method and apparatus for placing a finish on a material, such as metal, plastic, or wood. In particular, the method and apparatus are for placing on the material a finish that imitates a stone, such as marble.
2. Description of the Prior Art
It has long been a common practice to put a finish on an object in order to make the object appear to be made of a different material. For example, metal, plastic, or wood can be made to appear to be marble, granite, onyx, or other material. Thus, the aesthetic beauty of stone can be added to a different material having other desirable characteristics, such as high strength, low weight, or low cost.
U.S. Pat. No. 242,728 issued Jun. 7, 1881, to Withers, disclosed a method for giving a marble or granite appearance to several materials, including slate, stone, iron, wood, cloth, paper, papier-mache, leather, glass, porcelain, china, and crockery. The Withers method included first priming the material with paint. Then, a coating of color ground in water mixed with fermented liquor was applied. Next, while the coating was still wet, the coating was sprinkled with a hot solution of alkali. Finally, a varnish was applied as a finish or protective coat.
An automatic marbleizing apparatus was disclosed in U.S. Pat. No. 3,340,087, issued Sep. 5, 1967, to Mazzola. This apparatus creates a marble appearance by spraying a diluted material, such as lacquer, through a layer of disoriented material, such as steel wool. The substrate material could be pratically any material, such as stone, brick, metal, plastic, glass, wood, masonite, china, fabric, canvas, or leather. In order to protect the simulated marble effect, the treated material is sprayed with a coating of clear lacquer.
Although many methods of producing imitation stone finishes have been devised, most have been for low production or one-of-a-kind arts and crafts replication, primarily on organic substrates. None meets all of the desired criteria for replicating an imitation stone finish.
It is desired that an imitation stone finish meet five criteria. First the method of applying the finish should be suitable for three dimensional, pre-coated metal. The finish should be sufficiently durable to withstand packaging, handling, and normal fabrication methods. The finish should also be colorfast and consistently reproducible. Finally, the application method should be appropriate for high volume, automated production, where all of the steps are completed in one pass. None of the prior art methods meets all five of these criteria.